Ah, thanks for explaining!

Can someone ELI5 what impeachment even achieves, and why it seemed to do nothing last time? Is it just a badge of dishonour?

Exactly. In my opinion the best hope for the US is that the democrats fix their party in some amount via primaries, then win next election with a strong majority and immediately reform the electoral system to something better which allows for more parties.

No, len is a constant time operation, at least in most cases I believe.